Ixvili CHARLES OTIS WHITMAN 
The inquiry as to the origin of these patterns involves the main 
problem of the origin of species, for the general principles that 
account for one character must hold for others, and so for the 
species as a whole Darwin raised the same question, but did not 
pursue it beyond the point of trying to determine which pattern 
was to be considered original and how the derivation of the other 
was to be understood. Darwin’s explanation was so simple and 
captivating that naturalists generally accepted it as final. It is 
but fair to state that Darwin’s conclusions did not rest on a com- 
parative study of the color-patterns displayed in the many wild 
species of pigeons. Accepting the view generally held by natura- 
lists, that the rock pigeons must be regarded as the ancestors of 
domestic races, the question was limited to the point just stated.” 
Between the checkered and the barred types many intermediate 
stages may be found in different individuals. But which way is 
the series to be read, from checkers to bars or from bars to check- 
ers? Whitman finds an answer to this question in the evidence 
from experiments, from development, and from a comparative 
study of the Columbide. 
‘“‘ As an experiment, we may take one or more pairs of pure-bred, 
typically barred pigeons, and keep them isolated from checkered 
birds for several years, in order to see if the young ever advance 
toward the checkered type. 
‘Another experiment should be tried for the purpose of seeing 
what can be done by working in just the opposite direction. In 
this case we take checkered birds, selecting in each generation — 
birds with the fewer and smaller checkers, and rejecting the others, 
in order to see if the process of reduction can be carried to the 
condition of three, two, and one bar, and finally, to complete 
obliteration of both checkers and bars, leaving the wing a tabula 
rasa of uniform gray color. 
“Tf these experiments are continued sufficiently far, it will be 
found from the second experiment that a gradual reduction of 
pigment to the extreme conditions named can be comparatively 
easily effected, and that the direction of reduction will always be 
the same, from before backward; while, from the first experiment, 
